Center-fed whip antenna



Oct. 12, 1965 H. BRUECKMANN 3,212,093

CENTER-FED WHIP ANTENNA Filed July 2', 1963 FIG. 3 FIG, KQW s 26 BEFOREBREAK S% 30 l |4 UPPER RADIATOR |2\ 2 |4 I 12 FIG. 2 w i II 1/ UPPERRADIATOR JLQXEZTOR I 4 l u l K E .2 4 4 LOWER RADIATOR 4 L l3 l3 4 3' EJ '5 INVENTOR,

HELMUT BRUECKMANN. BY}? M! J J M Me J 0 UM/ 4 ATTORNEY:

United States Patent O 3,212,093 CENTER-FED WHIP ANTENNA HelmutBrueckmann, Little Silver, N.J., assignor to the United States ofAmerica as represented by the Secretary of the Army Filed July 2, 1963,Ser. No. 292,792 6 Claims. '(Cl. 343-724) (Granted under Title 35, U.S.Code (1952), see. 266) The invention described herein may bemanufactured and used by or for the Government for governmentalpurposes, without the payment of any royalty thereon.

The present invention relates generally to improvements in antennas andthe like and more particularly to a new and improved center-fed whipantenna wherein the antenna will continue to radiate energy after theupper section has been severed from the lower section.

The center-fed, vehicular, whip antenna is generally acknowledged assuperior in performance to the conventional base-fed, vehicular, whipantenna. Also, the center-fed whip antenna is more versatile than thebase-fed antenna since the characteristics of the former are independentof the type or place of mounting. For example, the center-fed antennaneed not be retuned when moved from one mount to another.

However, one criticism of prior center-fed, vehicular whip antennas isthat if the antenna were broken below the so-called feed-point and theupper section severed from the lower section, no radiation whatsoeverwould emit from the antenna.

The base-fed antenna will continue to radiate under these sameconditions; however, the efliciency will be reduced, of course, butsufficient energy will still be radiated to handle emergencycommunications.

This feature of continued radiation after the antenna has been broken isparticularly important in military equipment. For example, it is notuncommon for a tank to have its antenna broken in battle by enemygunfire, which results in effectively removing that particular tank froman operation.

It is therefore an object of this invention to provide a center-fed whipantenna which will continue to radiate energy even after the antenna hasbeen broken below the feed-point.

Other objects and features will become apparent from the followingdetailed description taken in connection with the accompanying drawingswhich form a part of this specification, and in which:

FIG. 1 is an elevation view of the antenna of the present invention;

FIG. 2 is a view similar to FIG. 1 but with a portion of the antennasevered; and

FIG. 3 is a sectional view of the antenna of FIG. 1 in the area of 3-3.

Referring to FIG. 1, there is shown an antenna having an upper section11, a lower section 12, and a base portion 13. The upper section 11 isremovably connected to the lower section 12 at section 14. Base portion13 comprises a flange 15 for mounting the antenna 10, and a threadedcoaxial connector 16 for connecting to a coaxial line leading from theradio set (not shown).

As seen in FIG. 3, the lower section 12 comprises a coaxial cable havingan outer conductor 20 and an inner conductor 21. The outer conductor 20is terminated at 22 while the inner conductor 21 extends therefrom.

The inner conductor 21 extends into the connector 23 which electricallyconnects the lower section 12 to the upper section 11. A recess 24 inconnector 23 recei es the inner conductor 21 which is held by and makesan electrical connection with a plurality of springs 25. These springs25 may be fastened in the recess 24 by soldering or any other well knownmethod.

3,212,093 Patented Oct. '12, 1965 ICC.

The outer conductor 20 of the coaxial cable will function as the lowerradiator of the whip antenna 10 with the effective feed-point located at22. Of course, this coaxial cable also functions as a transmission linefor feeding energy to the upper section 11.

Upper section 11 comprises a tubular conductor 26 having a threaded endportion 27 removably connected to a threaded socket 28 in connector 23.This conductor 26 will function as the upper radiator of the dipole withthe outer surface of conductor 20 acting as the lower radiator. Asstated before, the inner surface of conductor 20 and the inner conductor21 function as an R-F transmission line which feeds this dipole at 22.

The upper conductor 26 has a filling 30 of lightweight section 11 may beremoved from the lower section 12- at section 14. To prevent theconnector 23 from moving relative to the insulating material 31,projections 32 are provided which protrude into material 31.

, To provide for broadbanding of the antenna, the upper conductor 26 andthe lower conductor 20 should be made as wide as possible. Also, toprovide for easier matching and greater efliciency, the inner conductor21 should be made as thin as possible. Of course, the thicker theantenna, the better the chances are of its being severed by someprojectile. However, since the inner conductor 21 is relatively thin,and since it is protected to some degree by the outer conductor 22 andthe material 31, its chances of being severed by the projectile aresmall.

In the prior art devices, this inner conductor 21 would normally be tornby the severed portion of the antenna and the break would occur at anuncontrolled place. All that would usually be left standing would be aportion or all of the outer conductor 20 which, by itself, could notradiate any energy.

In the present antenna, shown in FIG. 3, the inner conductor 21 isconnected to the conductor 26 by the connector 23 which, because ofsprings 25, has only a frictional hold on the inner conductor 21. If theantenna should be severed somewhere below the feed point, connector 23will merely slip away from the inner conductor 21, thereby leaving aportion of this inner conductor 21 exposed to function as the upperradiator of the dipole, as shown in FIG. 2. Although the efiiciency ofthe antenna is now reduced, it will still be capable of radiating someenergy.

Of course, if the antenna is broken above the feed point 22, there willbe no problem since the remaining portion of the upper conductor 26 willstill function as the upper arm of the antenna.

If the antenna is broken near the base, thereby removing substantiallyall of the outer conductor 20, the center conductor 21 will stillradiate energy using the base 13 or the flange 15 as a counterpoise'.

The center conductor 21 should be made of a length such that, if theantenna should be severed at the feed point 22, there will be asutficient exposure of the inner conductor 21 to be capable of someradiation. The specific length will depend on the range desired and thedimensions of the antenna.

Since after the antenna is broken, the inner conductor 21 will be freeto move against the outer conductor 20, an insulating cover should beapplied to inner conductor 21. Also, the inner conductor 21 should alsohave some resiliency so as to snap up to a substantially verticalposition after the upper portion is severed. The inner conductor couldeasily and inexpensively be fabricated of a steel core covered with acopper layer followed by an insulating shell. The insulation, of course,should be omitted in the region where the springs 25 contact the innerconductor. It can therefore be seen that regardless of the point atwhich the present antenna may be broken, assuming, of course, that thehighly flexible and thin inner conductor 21 is not destroyed, radiationwill still be feasible.

It should be understood that the foregoing disclosure relates to only apreferred embodiment of the invention and that numerous modifications oralterations may be made therein without departing from the spirit andscope of the invention as set forth in the appended claims.

What is claimed is:

1. A center-fed whip antenna comprising; a lower conductor having atubular outer conductor and a flexible inner conductor mounted coaxiallytherewith and spaced radially therefrom, coaxial connector meansconnected to the lower end of said lower conductor for connecting autilization device from the lower end of said inner conductor to thelower end of said outer conductor; an upper conductor; and dielectricmeans mounting said upper conductor axially with said lower conductorand spaced from said outer conductor, said inner conductor at the upperend thereof extending axially a substantial distance beyond the upperend of said outer conductor and terminating in an electrical connectionwhich is mechanically weaker under tension than the tensile strength ofsaid inner conductor and said coaxial connector means, whereby when saidouter conductor is broken 011? the inner conductor will remain in placeand extend beyond the break to serve as a substitute antenna.

2. The antenna according to claim 1 and wherein said electricalconnection comprises a friction means for providing a relatively weakmechanical connection and a relatively good electrical connectionbetween said inner conductor and said upper conductor.

3. A center-fed whip antenna comprising upper and lower conductors; saidlower conductor having a tubular outer conductor and a flexible innerconductor mounted coaxially therewith and spaced radially therefrom,coaxial connector means connected to the lower end of said lowerconductor for connecting a utilization device from the lower end of saidinner conductor to the lower end of said outer conductor; the upper endof said inner conductor extending axially a substantial distance beyondthe upper end of said outer conductor; a metallic connector; said upperend of said inner conductor terminating in a friction connection withsaid metallic connector; and means on said metallic connector formounting said upper conductor in axial relationship with said lowerconductor and spaced from said outer conductor, whereby when a portionof said outer conductor is broken off the inner conductor will remain inplace and extend beyond the break to serve as a substitute antenna.

4. The antenna according to claim 3 wherein said friction connectioncomprises at least one spring finger mounted on said metallic connectorcontacting the upper end of said inner conductor.

5. The antenna according to claim 3 and wherein a resilient dielectriccover extends from said outer conductor to said metallic connector formaintaining said metallic connector spaced from said outer conductor.

6. The antenna according to claim 3 and wherein said inner conductorcomprises a thin, resilient rod covered by an insulating materialthroughout except for the upper end thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,379,577 7/45Harsted 343900 X 2,397,151 3/46 Mitchell 174-138 X 2,521,550 9/50 Smith343905 X 2,913,722 11/57 Brueckmann 343-729 2,945,084 7/60 Daggett343900 ELI LIEBERMAN, Primary Examiner.

1. A CENTER-FED WHIP ANTENNA COMPRISING; A LOWER CONDUCTOR HAVING ATUBULAR OUTER CONDUCTOR AND A FLEXIBLE INNER CONDUCTOR MOUNTED COAXIALLYTHEREWITH AND SPACED RADIALLY THEREFROM, COAXIAL CONNECTOR MEANSCONNECTED TO THE LOWER END OF SAID LOWER CONDUCTOR FOR CONNECTING AUTILIZATION DEVICE FROM THE LOWER END OF SAID INNER CONDUCTOR TO THELOWER END OF SAID OUTER CONDUCTOR; AN UPPER CONDUCTOR; AND DIELECTRICMEANS MOUNTING SAID UPPER CONDUCTOR AXIALLY WITH SAID LOWER CONDUCTORAND SPACED FROM SAID OUTER CONDUCTOR, SAID INNER CONDUCTOR AT THE UPPEREND THEREOF EXTENDING AXIALLY A SUBSTANTIAL DISTANCE BEYOND THE UPPEREND OF SAID OUTER CONDUCTOR AND TERMINATING IN AN ELECTRICAL CONNECTIONWHICH IS MECHANICALLY WEAKER UNDER TENSION THAN THE TENSILE STRENGTH OFSAID INNER CONDUCTOR AND SAID COAXIAL CONNECTOR MEANS, WHEREBY WHEN SAIDOUTER CONDUCTOR IS BROKEN OFF THE INNER CONDUCTOR WILL REMAIN IN PLACEAND EXTEND BEYOND THE BREAK TO SERVE AS A SUBSTITUTE ANTENNA.